magnum heads, 10.6 to 1 and a mild cam?

[moturbopar]

Hey all I have a .030 over 360 that has kb 107, magnum heads, with the .028 head gaskets its has .039 quench. the pistons and chambers have been polished and softened. Compression works out to 10.57 to 1. I have been looking at using my xe262 cam in this build, if I run it at 110 ic, dynamic compression shows it being at 8.45 to 1. Do you think this would work in a 3600lb vehicle, 2800 to 3000 stall, 3.73 gears and run on pump gas? If not i was thinking of going with an xe274. thanks

 

[Cuprum-74]

Aluminum or cast iron heads?

 

[moturbopar]

Iron heads.

 

[DartVadar]

I have a very similar setup to you, same bottom end, comp XE268 cam but alumimum eddy heads, runs like a champ with those heads, but you may be on the edge of pump gas with iron heads.

Also with my cam anyways (would be similar for you though) its a dogggg with my current gears off the line. I havent changed out the 2.76 rears yet, It needs at least 3.55 to run good off the line, I am going with 3.91s. The 3.73 with that converter should be a good combo though.

 

[rumblefish360]

10.6-1 is pretty high there buddy. Start with 93 octane. I'm crossing my fingers for you.

 

[moturbopar]

yep pushing it for sure! The vehicle doesnt get many miles a year, so if needed I can run some kind of octane booster. Would you guys go with a bigger cam? its going to be street strip, weekend cruiser. not a daily driver.

 

[rumblefish360]

Is so at least the 3/73 & the 268. Next cam size up would be my personal pick for a street machine and your parts.

Skip any octane booster.

 

[71DodgeDemon340]

Comp is a little to high for 93 10:1 is even on the high side for pump gas 9.5:1 is more ideal

 

[RustyRatRod]

You will have problems with iron heads and that high of a dynamic compression ratio. Get it under 8:1 and you should be good.

 

[mderoy340]

I built my J head 340 to 8.2 dynamic and it runs great on 93. Knocked down all edges on pistons, smoothed combustion chambers and got all chambers the same CCs, 34* total timing. Pick another cam with a later IVC point and get the dynamic down. I hope you are CCing everything yourself. Piston specs from the manufacturer usually are not correct due to deck height variables.

 

[MopaR&D]

Those gears and stall can definitely handle a bigger cam I would go with the XE274 for sure; your dynamic CR with that should be down around 8:1 which is safe for pump gas.

Just curious did you have the valve guides machined down for more lift clearance? Also I'm assuming you're using factory 1.6:1 rockers? That XE274 will have far too much lift with 1.6 rockers on stock Magnum heads if the guides aren't machined.

 

[moper]

I'm fairly sure your inputs to the calculator you're using are wrong. You will have a dynamic well over 9:1 with that cam. The other issue is the metioned valve springs and limited lift on factory type Magnums. There's not enough spring to go much bigger - so you have a problem.

 

[moturbopar]

I have been using the wallaceracing calculator for the dcr calculations. Still shows the same calculations. Don't forget that I have the ivc (61) set 4 deg retarded from the 106cl comp grinds them on. As for the heads I have adjustable valve train, roller rockers. The heads are good to .540 lift. At .540 lift I have .050 clearence between retainer and valve seal.

 

[fishy68]

I wouldn't take a chance with a cam that small nor would I retard it to "try to make it work". I'd go with the XE274 is I were wanting to use a Comp cam. Naturally the 274 will idle choppier than the 262

 

[moturbopar]

That's what I'm thinking. Is there another cam you all would recommend? Not worried about vacuum but don't want to lose too much drivability, might see 2500 miles a year.

 

[sst3193]

I love the XS 274 and would expect it to be doable at 10.5. I'm running it in a .03 over 360, w/iron heads and put nothing but 87 octane regular in it.

 

[Abodybomber]

WhAt are you running for exhaust? Is gas mileage a big thing? This is your truck?.

 

[moturbopar]

Yes this is my truck, I was going to put another engine in it, unfortunatly had to sell it off to pay some bills. So I am back to my original 360. Anyways Im using long tube 1 5/8 headers, into 3" tubes, x pipe and 3" race bullets. Not too worried about fuel economy. No emmisions
also have a 4.10 rear axle if needed.

 

[Leadfoot]

I'd toss that 262 in the car without a second thought. I have a solid 11:1 and a Crane with roughly the same specs. I run on 85 octane all day long. Of course being up here at 5000 feet helps. Take in to consideration that furnace you live in will offset the altitude as far as air density.

 

[Abodybomber]

Yes this is my truck, I was going to put another engine in it, unfortunatly had to sell it off to pay some bills. So I am back to my original 360. Anyways Im using long tube 1 5/8 headers, into 3" tubes, x pipe and 3" race bullets. Not too worried about fuel economy. No emmisions
also have a 4.10 rear axle if needed.

Absolutely, a big exhaust can help deduce detonation. {Think about it)....
A short intake charge,with an extended duration with a good exhaust port.Extends the R.P.M.'s Inc creasing torque. .(Where I learned).,...

 

[moturbopar]

Thanks guys, I m just going to save or try and sell the xe262 again. Im leaning towards Comp xe275hl or lunati voodoo 276 and use 1.5 ratio rockers.

 

[fishy68]

I didn't realize this is a truck you have. That changes things due to the extra weight needing as much torque as possible. But also keep in mind that extra weight loads the engine more which can make it spark knock worse so it's a catch 22. If it were me I wouldn't be looking at off the shelf cams. I'd call a few cam grinders and get some recommendations. There are a lot of great cam grinders out there that know what works best in every scenario. Racer Brown, Bullet cams, Oregon cam grinders, Clay Smith just to name a few. Most of the time custom cams don't cost much (if any) more than an off the shelf cam.